Aadhaar No, originally the Unique Identification Number, an initiative of the Unique Identification Authority of India (UIDAI) of the Indian Govt to create a Unique ID (XXXX XXXX XXXX) for every Indian resident

UID Full form – Unique Identification
UIDAI Full form – The Unique Identification Authority of India

UIDAI is a statutory authority established on 12 July 2016 by the Government of India under the Ministry of Electronics and Information Technology, under the provisions of the Aadhaar Act 2016. The UIDAI is mandated to assign a 12-digit unique identification (UID) number (termed as Aadhaar) to all the residents of India.